Polymer Journal (2012) 44, 217–223 & 2012 The Society of Polymer Science, Japan (SPSJ) All rights reserved 0032-3896/12 www.nature.com/pj ORIGINAL ARTICLE Terephthalaldehyde- and isophthalaldehyde-based polyspiroacetals Hayal Bulbul Sonmez1, Figen Gonul Kuloglu1, Koksal Karadag1 and Fred Wudl2 Condensations of polyhydroxyl monomers with terephthalaldehyde or isophthalaldehyde give the corresponding polyspiroacetals. The effects of various dialdehydes and multihydroxy monomers on the properties of the resulting polymer have been examined. Model compounds were synthesized by the condensation of multihydroxy monomers with benzaldehyde. The model compounds and polymers were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance (NMR), thermogravimetric analysis and differential scanning calorimetry. The proposed polymer structure is supported by the solid-state CPMAS 13C NMR spectrum of the model compound. The synthesized polyspiroacetals are thermally stable, have a high degree of chemical stability and are soluble in hexafluoroisopropanol. Polymer Journal (2012) 44, 217–223; doi:10.1038/pj.2011.126; published online 14 December 2011 Keywords: isophthalaldehyde; polyspiroacetal; terephthalaldehyde INTRODUCTION solvents from the reaction of pentaerythritol with an alkyl-bearing Ladder polymers have been pursued by many researchers because their diketone. rigidity results in a lack of rotational freedom and good thermal and Previously, we synthesized a spiro polymer by the reaction of chemical stability.1 Spiro polymers are a subclass of ladder polymers 1,1,4,4-tetrakis(hydroxymethyl)cyclohexane and terephthalaldehyde where two adjacent rings share an atom.1,2 Ladder and spiro polymers in toluene in the presence of a trace amount of acid.3 In this study, are therefore of particular interest because they generally possess a series of spiro polymers based on terephthalaldehyde and isophtha- increased resistance to degradation compared with conventional laldehyde was synthesized to examine the effects of different dialde- polymers.2,3 hyde and multihydroxy monomers on polymer properties. The first organic spiro polymer was synthesized by the reaction of 4 1,4 cyclohexanedione and pentaerythritol in the presence of an acid. EXPERIMENTAL PROCEDURE This polymer was thermally stable and crystalline. A number of other Reagents and equipment polyspiroketals were also prepared by the condensations of various The highest purity grade of each chemical available from Aldrich (Taufkirch- cyclic diketones and tetraols, resulting in polymers with good chemical enbei Mu¨nchen, Germany) was used without further purification. and thermal stabilities.5 Several spiroacetals were prepared by the Fourier transform infrared spectroscopy (FT-IR) spectra were recorded on a reaction of carbonyl compounds and multihydroxy monomers. Cohen Bio-Rad FTS 175C FT-IR spectrophotometer (Bio-Rad, Hercules, CA, USA) and coworkers synthesized thermoplastic polyspiroacetal resins using using KBr pellets. 13C solid-state nuclear magnetic resonance (NMR) spectra dialdehydes with pentaerythritol or pentaerythritol–dipentaerythritol were recorded on a 500-MHz Varian Inova spectrometer (Varian, Palo Alto, mixtures. Not surprisingly, these polymers had limited solubility in CA, USA) in a magic angle spinning (MAS) probe at 75.476 MHz. Thermo- common solvents and exhibited high melting points.6 Later, the same gravimetric analysis (TGA) was performed under a nitrogen atmosphere at 101CminÀ1 with a Mettler Toledo model TGA/SDTA 851(Mettler Toledo, group prepared spiro polymers and copolymers derived from pentaer- 7 Greifensee, Switzerland). Differential scanning calorimetry (DSC) was per- ythritol, dipentaerythritol and glutaraldehyde. Results show that formed with a Mettler TA Instrument DSC 822 at a heating rate of 10 1CminÀ1 spiroacetal unit-bearing polymers exhibited excellent mechanical under a nitrogen atmosphere. properties, including high strength and hardness as well as heat and water resistance.8 In general, the high melting points and low Synthesis of the monomers solubilities of spiroacetals indicate strong inter-chain forces and Synthesis of 2,2,6,6-Tetrakis(hydroxymethyl)cyclohexanone. This compound a high degree of order. Recently, a series of new cyclic acetals of was synthesized according to Mannich and Brose.11 m.p.: 142.6–143.5 1C. Mass 2-hydroxybenzaldehyde has been investigated for a correlation m/z (M+Na): 241 g molÀ1. FT-IR: 3370, 2940, 2875, 1690, 1061 and 1000 cmÀ1. 9 1 d6 between the acetal structure and its biological activity. Makhseed H-NMR (DMSO ): d (p.p.m.): 4.46 (-CH2OH), 3.5–3.3 (Cquaternary-CH2- 10 and McKeown prepared a spiro polymer that was soluble in organic OH) and 1.8–1.7 (-C(¼O)-Cquaternary-CH2- and -C(¼O)-Cquaternary-CH2-CH2-). 1Department of Chemistry, Gebze Institute of Technology, Kocaeli, Turkey and 2Department of Chemistry and Biochemistry, University of California, Santa Barbara, CA, USA Correspondence: Professor HB Sonmez, Department of Chemistry, Gebze Institute of Technology, PO Box 141, Kocaeli, Gebze 41400, Turkey. E-mail: [email protected] Received 25 July 2011; revised 27 September 2011; accepted 1 October 2011; published online 14 December 2011 Terephthalaldehyde- and isophthalaldehyde-based polyspiroacetals HB Sonmez et al 218 13 d6 CNMR:(DMSO ): d (p.p.m.): 218 (C¼O), 64 (CH2-OH), 55 (C, quatern- Synthesis of Model 3: 3,11-diphenyl-2,4,10,12-tetraoxa-dispiro[5.1.5.2]pentade- ary), and 28 and 17 (-C(¼O)-Cq-CH2-and-C(¼O)-Cq-CH2-CH2-). can-7-one. A 100-ml round-bottomed flask equipped with a magnetic stirrer, a Dean–Stark trap and a reflux condenser was charged with 1 g (4.9 mmol) Synthesis of 2,2,6,6-Tetrakis(hydroxymethyl)cyclohexanol. This compound was 2,2,5,5 tetrakis(hydroxymethyl)cyclopentanone in 2 ml NMP, 1 ml (9.8 mmol) synthesized according to Witcoff.12 m.p.: 127–132 1C. Mass m/z (M+Na): benzaldehyde, 20 mg methane sulfonic acid and 50 ml benzene. The mixture 243 g molÀ1. FT-IR: 3497, 3267, 2954, 1400, 1016 and 776 cmÀ1. 1HNMR was heated under reflux until no more water was collected in the Dean–Stark 6 (DMSO-d ): d (p.p.m.): 4.66 (CH-OH), 4.48 (CH2-OH), 3.71 (CH-OH), 3.55 trap, followed by cooling to room temperature. The resulting precipitate was 13 6 and 3.45 (CH2-OH), and 1.5 and 1 (-CH2). C NMR (DMSO-d ): d (p.p.m.): collected by filtration and washing with a 5% sodium bicarbonate solution and 76 (-CH-OH), 67 and 62 (-CH2-OH), 43 (C, quaternary), 27 and 16 ether. The residue was crystallized from ethanol:benzene (95:5) to give 0.56 g (-HOCtertiaryH-Cq-CH2- and (-HOCtertiaryH-Cq-CH2-CH2-). (30%) of 3,11-diphenyl-2,4,10,12-tetraoxa-dispiro[5.1.5.2]pentadecan-7-one. m.p.: 203 1C. Mass m/z:403gmolÀ1 (M). FT-IR: 3300, 2975, 2860, 1715, À1 1 Synthesis of 2,2,5,5-Tetrakis(hydroxymethyl)cyclopentanone. This compound 1465, 1105, 760 and 690 cm . H NMR (CDCl3), d (p.p.m.): 2.4 (CH2, 13 1 was synthesized according to Ray. m.p.: 145.9–147.5 C. Mass m/z (M+Na): cyclopentane ring), 3.9 (CH2-O), 5.5 (CH-O) and 7.3–7.6 (benzene ring). À1 À1 1 13 227 g mol . FT-IR: 3200, 2960, 2888, 1725 and 1045 cm . H NMR (DMSO- C NMR (CDCl3), d (p.p.m.): 29 (CH2,cyclopentanering),53(C, quaternary, 6 13 d ): d (p.p.m.): 4.59 (CH2-OH), 3.43–3.24 (CH2-OH) and 1.97 (-CH2-). C cyclopentane ring), 71.5 (CH2O), 101 (CHO2, acetal), and 125, 130 and 138 6 NMR (DMSO-d ): d (p.p.m.): 222 (C¼O), 62 (Cq-CH2-OH), 59 (C, quatern- (benzene ring). ary) and 24 (-C(¼O)-Cq-CH2 or -C(¼O)-Cq-CH2-CH2-). Synthesis of 1,4 dicarbaldehydecyclohexane. This compound was synthesized Synthesis of Model 4: 3,12-diphenyl-2,4,11,13-tetraoxadispiro[5.2.5.2]hexadeca- according to Feuerbacher et al.14 FT-IR: 2938, 2857, 1715, 1445, 1136 and ne. A 100-ml round-bottomed flask equipped with a magnetic stirrer, a À1 1 915 cm . H-NMR (CHCl3): d (p.p.m.): 1.31–1.37 (CH2), 1.74–1.80 (CH2), Dean–Stark trap and a reflux condenser was charged with 0.5 g (1.9 mmol) 2.10–2.2- (CH2) and 9.60–9.63 (CHO). 1,1,4,4-tetrakis(hydroxymethyl)cyclohexane in 1 ml dimethyl sulfoxide (DMSO), 0.39 ml (3.8 mmol) benzaldehyde, 20 mg methane sulfonic acid Synthesis of 1,1,4,4-Tetrakis(hydroxymethyl)cyclohexane. This compound was and 50 ml benzene. The mixture was heated under reflux until no more water synthesized according to Herwig et al.15 using cis,trans-cyclohexane-1,4-dicar- was collected in the Dean–Stark trap, followed by cooling to room temperature. baldehyde and formaldehyde. The resulting product was recrystallized from The resulting precipitate was collected by filtration and washing with a 5% ethyl acetate. m.p. 222 1C (reported 219–225 1C). Mass m/z (M+Na): sodium bicarbonate solution and ether. The residue was crystallized from 227 g molÀ1. FT-IR: 3370, 2904, 2842, 1070, 1017 and 672 cmÀ1. 1H-NMR ethanol to give 0.34 g (54%) of 3,12-diphenyl-2,4,11,13-tetraoxadispir- d6 13 1 À1 (DMSO ): d (p.p.m.): 4.26 (OH), 3.38 (-CH2-OH) and 1.2 (CH2). CNMR: o[5.2.5.2]hexadecane. m.p.: 208–210 C. Mass m/z:381gmol (M). FT-IR: d6 À1 1 (DMSO ): d (p.p.m.): 65.2 (CH2-OH), 39.8 (C, quaternary) and 24.2 (CH2, 3300, 2978, 2808, 1123, 1034, 1010, 755 and 690 cm . H NMR (CDCl3), cyclohexane ring). d (p.p.m.): 1.23 (CH2, cyclohexane ring), 1.8 (CH2, cyclohexane ring), 3.9 13 (CH2-O), 5.32 (CH-O) and 7.0–7.8 (benzene ring).